The Socialist Unity Party of Germany (SED) (German: Sozialistische Einheitspartei Deutschlands) was the governing party of East Germany from 1949, when East Germany was created, until the elections of 1990.

A famous SED poster read: To learn from Stalin means to learn how to win. Later, the word Stalin was replaced with the USSR. When Gorbachev was president of the USSR the famous slogan was abandoned, as the SED did not believe there was anything to learn from his ideas about perestroika.

Between the fall of the Berlin Wall in November 1989 and the election in March 1990, the old Social Democratic Party was re-established as a separate party, while the rest of the SED lost a lot of members and renamed itself the Party of Democratic Socialism (PDS) at a special party meeting in December 1989. By becoming the PDS the party survived the reuniting of East Germany any West Germany, and eventually started growing again, managing to get representatives elected to the Bundestag.